The 3rd Generation Partnership Project, 3GPP, is responsible for the standardization of the Universal Mobile Telecommunication System, UMTS, and Long Term Evolution, LTE. The 3GPP work on LTE is also referred to as Evolved Universal Terrestrial Access Network, E-UTRAN. LTE is a technology for realizing high-speed packet-based communication that can reach high data rates both in the downlink and in the uplink, and is thought of as a next generation mobile communication system relative to UMTS. In order to support high data rates, LTE allows for a system bandwidth of 20 MHz, or up to 100 MHz when carrier aggregation is employed. LTE is also able to operate in different frequency bands and can operate in at least Frequency Division Duplex, FDD and Time Division Duplex, TDD, modes.
In 5G, i.e. 5th generation mobile networks, there will be evolvement of the current LTE system to 5G. One of the main tasks for 5G is to improve throughput and capacity compared to LTE. This is achieved by increasing the sample rate and bandwidth per carrier. 5G is also focusing on use of higher carrier frequencies i.e. above 5-10 GHz.
When a UE is switched on for the first time it will start searching for a network. The UE synchronizes to each frequency and checks whether this is a frequency from an operator to which it wants to connect. Once synchronized, the UE reads the Master Information Block, MIB, and System Information Blocks, SIBs, to check whether this is the right Public Land Mobile Network, PLMN. Following the reading, the next step is a random access procedure which allows the network to know that a UE is trying to get access. At this stage, the UE does not have any resource or channel available to inform the network about its desire to connect to, so a request will be sent over a shared medium.
The MIB only includes a very limited part of the system information. The main part is included in different SIB:s that are transmitted using the Downlink Shared Channel, DL-SCH. The presence of system information on DL-SCH in a subframe is indicated by the transmission of a corresponding Physical Downlink Control Channel, PDCCH, marked with a special System-Information Radio Network Temporary Identifier, RNTI. This PDCCH indicates the transport format and physical resource (set of resource blocks) used for the system-information transmission. There are a number of different system information blocks that are broadcasted repeatedly.
Future telecommunication systems will benefit from a lean design where the transmission of broadcast signals like MIB, SIB, or similar, and synchronization and common reference signals are only transmitted when necessary, i.e. when they are actually needed for measurements by one or several devices. The main reason for this is to reduce unnecessary interference as well as reduce the radio network node power consumption. A concept called System Control Plane, SCP, is introduced where a macro site broadcast the necessary system information on a frequency carrier. Other macro frequency carriers or high layer small sites within the macro site coverage do not need to broadcast all system information. These sites only need to broadcast a small System Signature Indication, SSI, pilot. If a UE make access to a site/carrier which only broadcast SSI, the UE use the broadcasted system information received from the macro site, by mapping the SSI to the right system information.
Even if the system and UE support the possibility to minimize the broadcast load, a pre-requisite to utilize the concept is that the system can be configured correctly, i.e. to configure transmission points and frequency carriers so that redundancy or sufficient coverage from other transmission points and frequency carriers is provided to enable that system information broadcast can be turned off of from a first set of transmission points and frequency carriers.
A good deployment plan of the system information broadcast plan is very complex without availability of good feedback information, which is currently not specified. Thus, there is a need in the art for improved feedback to enable a more resource efficient system design for broadcasting system information; a system design using an optimal set of transmission points and frequency carriers for system information broadcast.